A brassiere or swimsuit top typically has a pair of cups from which so-called wings extend around the back of the wearer. The ends of the wings are typically joined together at a closure that is also usually set up to adjust the length of the brassiere back.
The most common back adjuster/closure is comprised of at least one row of eyes provided on one of the wings and at least one hook on the other wing. Big brassieres have several rows of eyes and a complementary number of hooks. The fit of the brassiere is adjusted by determining which eye (or set of eyes) the hook (or hooks) is/are fitted to.
This arrangement has several disadvantages. To start with the user must determine which eyes to use each time the garment is donned, even though the setting is rarely changed. Even if the brassiere or garment has a front closure, so that the rear adjuster does not have to be opened up to take off or put on the garment, the hook/eye system can open relatively easily when not under tension. When such a garment is washed, the hooks can get caught in and damage other items in the load of wash. In addition the assembly is fairly bulky and includes several metal or hard plastic parts that form a perceptible lump under the wearer's outer garments, a problem aggravated by the fact that only part of the adjuster is actually doing anything.